Centrifugal switch.



1. R. COOK.

CE NTRIFUGAL SWITCH.

APPLICATIONFILED FEB. n. 1913.

1,26 1,1 02. Patented A 2, 1918.

2 SHEET EET l.

J. R. COOK.

CENTRIFUGAL SWITCH.

APPLICATION FILED FEB. 17. 1913.

Patented Apr. 2, 1918.

2 SHEETSSHEET Z.

UNITED STATES PATENT OFFICE.

JOEL COOK, OF'WIIIKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELEC- TBIC AND MANUFACTURING COMPANY, CORPORATION OF PENNSYLVANIA.

CENTRIFUGAL SWITCH.

Specification of Letters Patent.

Patented Apr. 2, 1918.

Application filed February 17, 1913. Serial No. 748,858.

new and useful Improvement in Centrifugal Switches, of which thefollowing is a specification.

My invention relates to centrifugal switches such as "are commonly employed in electrical devices in which circuit connections are made and interrupted at predetermined speeds and it has special reference to fan motors of the single phase alternating current induction type and to starting means therefor.

The object of my invention is to provide a switching device of the character indicated above'which shall be simple and durable in construction. and positive and certain in its action under all conditions.

It is desirable, in practice, to provide sin- My invention provi es a centrifugally. operated switch by means of which the circuit ofthis auxiliary winding is automati cally broken when a predetermined speed is reached and automatically closed again upon the speed falling oil to a predetermined minimum, or when the motor stops.

' In the drawings, Figure 1 is a front view of an induction .motor with my invention applied, part of .the end bracket of the motor being broken away. Fig. 2 is a side view of the same, partly in section, on the line II- II' of F1g...1. Fig. 3 is a front elevation of the centrifugal device attached to the rotor of a motor, the cams being in their extendedpositions 'Fi 4 is a longitudinal section on the line I" -IV of Fig. 3, part of'therotor beingibroken away. Fig.5 is a front elevation of-thestationary member of theswitch". :SFig. 6 is a diagram. of the motor windings and the switch. I Fig. 7 is a front elevation; .partiall I in section, of a modificationoftheswitc The induction motor 1 has a rotor 2. upon ing a circular flange 8 extending outwardly and upon which is rotatably mounted a second plate 9. The relative movement of the,

plates 3 and 9 is limited by springs 10 severally attached at one end to lugs 11 on the plate 3 and at the other end to projections 12 on the plate 9 which are bent at right angles to project through slots 13 in plate 3. Curved arms or cams 14 are pivotally mounted at 15 upon the plate 3 and are adapted to overlap each othenby being bent in an intermediate portion as shown at 51 in Fig. 4:, so that the corresponding ends of each cam lie in the same place, while the opposite ends, which they overlap,'lie in a parallel plane. Any desired number of cams may be employed, four being shown in the preferred form of my invention. The cams are so curved that approximate circles are presented by'their combined outer peripheries and combined inner peripheries in any position assumed by the cams as they are actuated by centrifugal force.

The plate 9 has four projecting arms 16 bent at right angles at the ends 17 to extend through inclined slots 18 in the cams 14. This construction insures that any movement of the cams ontheir pivots .will cause a corresponding rotative movement of the plate 9 and that the movement of each of the cams is the same because of their interconnection- I The movement of the cams is also limited -in extent by the slots 18 and members 17. I

The stationary member of the switch is located upon a stationary part 19 of the motor and, in one of the preferred forms, asshown in Fig. 5, comprises an arm 20 pivoted at 21, -to a supporting member 22 attached to an insulating base 23. A spring 24'is connected at 25; to the sup orting mem-' her 22 and to the contact mom or 26 at 27. It, will be noted that thearm 20 is in unstable equilibrium when the points, 27, 21-

Owing to the peculiar shape and arrangement of the various arts, the switch is adapted to make and reak the circuits at a point apart from the point designed to make the normal contact for the passage of current.

It will be noted that the contact pieces are of approximately L-shape. When the contacts are brought together, the portions 31 and 32 make contact first by reason of the position in which contact member 26 is held by the spring 24, but theforce of the spring is suflicient to swing the arm 20 still farther until surfaces 33 and 34 are in engagement. The contact will be a sliding one because of the rotative movement of the contact member/26 after the engagement of portion 31 and. 32, thus insuring clean surfaces and a good electrical contact. Upon the switch being open, the parts 33 and 34 will be separated first by the rotative move ment of the contact member 21, since the spring 24 tends to place the points 29, 27 and 25 in alinement. This actlon will cause any arcs incident to the make and break to take place between parts 31 and 32. A yoke 35 is attached to the switch arm 20, and its arms .36 span the cams 14. Terminals 37 and 38 are provided which connect the contact members 30 and 26 to the auxiliary winding 39 and one of the motor terminals, respectively, the other terminal of the auxiliary winding being connected pera manently to the other terminal of the motor. The main motor winding is shown at 40 in Fi .6. Y

A modification of the stationary member is shown in Fig. 7 in which the same numerals are used to designate like parts. An arm 41 is preferably integral with the arm 20 while an arm 42 is ivoted at 43 and normally held against a s oulder 44, as shown,

by'the spring 24'which holds a 'pivotally vmounted contact member 45 with its shoulder 46-against a projection 47 of the arm 42.

A contact member 48 has a concave surface against the surface of contact member 48 as 49 which is adapted to beengaged'by'a convex surface 50 of the contact member 45. When the arm 42 is actuated by the cams 14, it tends to assumes. radial position which causes it to rotate in the direction of'the arrow, and the contact member 45 is pressed the arm 20' is moved outward, thus insuring a sliding or wiping contact and the breaking of the contact at a point normally not engaged by contact 48i This modification op crates as a toggle snap switch inthe same manner as :the structure shown in Fig. 5.

When the motor circuit isclosed through cams 14 to fly outward against the tensionof the springs 10 exerted through the plate. 9 and the members 17 and inclined slots 18, and the outer peripheries of the cams will .take the position shown in Fig. 3 and engage the yoke ,35. The tension of the springs 10 may be adjusted to allow the cams to operate at any predetermined speed to actuate the arm 20 outwardly until it passes its central position, when the spring 24 carriesit to its outer position, separating the contacts and breaking the circuit of the auxiliarywinding. The cams do not engage the arms when the motor is rotatin because of the position takenby the switc arm 20 and the distance between the arms. The outer and inner positions of the yoke arms are shown in section in Figs. 3 and 1, respectively. When the motor slows down or stops, the springs 10 will cause the cams to contract and the inner peripheries of the cams will take the position shown in Fig. 1,- and engage the yoke 35, and the arm 20 will swing inwardly and again complete the circuit of the auxiliary winding ready for ac celeration or startin The advantages 0% this construction will be apparent to one skilled in the art as the action is positive and automatic at anydesired speed, a continuous surface is presented by the cams, and provision is made for clean contact surfaces for the switch. Because of the circular form presented by the cam surfaces in both the expanded and contracted positions, the actuation of the switch arm is accomplished easil and'gradually and the striking of a blow y rotating parts is avoided. 3

While only oneapplication of m improved switch has been shown, it is a apted to be'usedin connection with any rotatable device inwhich it is desired to make or break a circuit at any desired speed.

,I claim as my invention:

1. The combination with a rotatable shaft, of a switch, and an expansible mechanism carried by said shaft and adapted to open sa d switch by expanding at a predetermined -s cod and to close said switch by contractmg at another predetermined of rotation of said shaft.

2. The combination with a rotatable shaft, of a stationary tog 'le switch, and a mechanism carried by and shaft and capable of having both internal and external engagement with said switch and adapted to open 'said switch at a predetermined speed and to close said switch at another speed of rotation of said shaft.

3. The combination with a rotatable shaft having a centrifugal device mounted thereon, of a stationary switch mounted so as to .be engaged both by the inner and by the predetermined.

outer periphery of the centrifugal device, both of said peripheries presenting substantially circular surfaces.

4. The combination with a rotatable shaft, of a stationary toggle snap switch, an expansible ring-like mechanism carried by said shaft, and a member on said switch adapted to be engaged by the inner and by the outer eriphery of said mechanism to open and c ose said switch at redetermined speeds of rotation of said she t.

5. In combinatioma supporting member adapted to rotate, a plura ity of cams pivoted to said member and adapted to be thrown outwardly b centrifugal force, said cams being arrange to overlap each other, a plate member rotatably mounted on said supportin member, projections on said plate member adapted to engage slots in said cams and means for yieldingly holding said plate member in one position relative to said supporting member.

6. In combination a rotatable supporting member, a plurality of centrifugally actuated cams pivoted on said member and arran ed to overlap each other, said pivots belng mounted concentric with the axis of rotation, amember rotatably mounted on said supporting member and engaging each of said cams in an inclined slot, and means for yieldingly holding said engaging member in one position.

7 The combination with a rotatable shaft, of a composite ring carried thereby, said ring being adapted to increase in diameter Y with an increase in the speed of rotation of said shaft and to decrease in diameter with a decrease in the speed of said shaft, a switch, means for biasing said switch to either the open or the closed position and operatin members carried b said switch, one of w ich is mounted to e engaged by the outer surface of said ring to move said switch to one position and the other of which is mounted to be engaged by the inner surface of said ring to move said switchto the other position.

8. The combination with a rotatable shaft of a composite ring carried thereby, said ring being adapted to increase in diameter with anincrease in the speed of rotation of said shaft and to decrease in diameter with a decrease in the speed of said shaft, a stationary toggle snap switch, and operating members carried by said switch, one of which is mounted to be engaged by the outer surface of said ring to move said switch to One position and the other of which is mounted to be engaged by the inner surface of said ring to move said switch to the other position.

9. The combination with arotatable shaft having a centrifugal device mounted thereon, of a stationary switch mounted to be engaged both by the inner and by the outer periphery of the centrifugal device, both of said peripheries presenting substantially circular surfaces, said centrifugal device being adapted to open and close said switch at predetermined speeds of rotation of said shaft.

10. The combination with a stationary switch, of a rotatable mechanism for operating the same, comprising an expanding and contracting ring adapted to engage said switch by means of its external and internal peripheries. 4 y

In testimony whereof, I have hereunto subscribed my name this 7th day of Feb., 1913.

JOEL R. cooK.

Witnesses:

.J. R. LANGLEY, B. B. HINES. 

